| Message ID | 20120628084509.4caec81d@kryten |
|---|---|
| State | Superseded |
| Headers | show |
On Thu, 2012-06-28 at 08:45 +1000, Anton Blanchard wrote: > hard_irq_disable(); > - if (get_paca()->irq_happened == 0) > + if (get_paca()->irq_happened == PACA_IRQ_HARD_DIS) > cede_processor(); I'd rather add a helper, something like lazy_irq_pending() and hide the actual check for the bits in irq_happened, in case we change the scheme again. Something like: static inline bool lazy_irq_pending(void) { return !!(get_paca()->irq_happened & ~PACA_IRQ_HARD_DIS); } Cheers, Ben.
Index: linux-build/arch/powerpc/platforms/pseries/processor_idle.c =================================================================== --- linux-build.orig/arch/powerpc/platforms/pseries/processor_idle.c 2012-06-27 21:20:45.403761715 +1000 +++ linux-build/arch/powerpc/platforms/pseries/processor_idle.c 2012-06-27 21:57:14.796788823 +1000 @@ -106,7 +106,7 @@ static void check_and_cede_processor(voi * we first hard disable then check. */ hard_irq_disable(); - if (get_paca()->irq_happened == 0) + if (get_paca()->irq_happened == PACA_IRQ_HARD_DIS) cede_processor(); }
Commit f948501b36c6 ("Make hard_irq_disable() actually hard-disable interrupts") caused check_and_cede_processor to stop working. ->irq_happened will never be zero right after a hard_irq_disable so the compiler removes the call to cede_processor completely. The bug was introduced back in the lazy interrupt handling rework of 3.4 but was hidden until recently because hard_irq_disable did nothing. This issue will eventually appear in 3.4 stable since the hard_irq_disable fix is marked stable, so mark this one for stable too. Signed-off-by: Anton Blanchard <anton@samba.org> Cc: stable@vger.kernel.org ---